Transseptal cannula, tip, delivery system, and method

ABSTRACT

A cannula assembly, further comprising a cannula body for directing blood from the heart of a patient, having distal and proximal ends and a lumen therebetween. A tip coupled to the distal end of the body, the tip having an opening. A pump for drawing blood into the cannula assembly and dispensing the blood from the cannula assembly and into the patient circulatory system. The lumen of the cannula body further comprises a first inner diameter at the proximal end and a second inner diameter at the distal end, the first inner diameter being larger than the second inner diameter. A tapered portion defined as a decrease in inner diameter from the first inner diameter to the second inner diameter between the proximal and distal ends, the tapered portion configured to prevent cavitation of the blood within the cannula.

This application is a continuation-in-part of application Ser. No.13/088,620, filed Apr. 18, 2011 (pending) which is a divisional ofapplication Ser. No. 12/256,911, filed Oct. 23, 2008 (now U.S. Pat. No.8,343,029), which claims the priority of Provisional Application Ser.No. 60/982,322, filed Oct. 24, 2007, the disclosures of which areincorporated by reference herein.

BACKGROUND

The human heart is the muscle that is responsible for pumping bloodthroughout the vascular network. Veins are vessels that carry bloodtoward the heart while arteries carry blood away from the heart. Thehuman heart consists of two atrial chambers and two ventricularchambers. Atrial chambers receive blood from the body and theventricular chambers, which include larger muscular walls, pump bloodfrom the heart. A septum separates the left and the right sides of theheart. Movement of the blood is as follows: blood enters the rightatrium from either the superior or inferior vena cava and moves into theright ventricle. From the right ventricle, blood is pumped to the lungsvia pulmonary arteries to become oxygenated. Once the blood has beenoxygenated, the blood returns to the heart by entering the left atrium,via the pulmonary veins, and into the left ventricle. Finally, the bloodis pumped from the left ventricle into the aorta and the vascularnetwork.

For the vast majority of the population, the events associated with themovement of blood happen without circumstance. However, for many peoplethe heart fails to provide adequate pumping capabilities. These heartfailures may include congestive heart failure (commonly referred to asheart disease), which is a condition that results in any structural orfunctional cardiac disorder that impairs the ability of the heart tofill with or pump blood throughout the body. Presently, there is noknown cure for heart disease and long-term treatment is limited to aheart transplant. With only a little over 2,000 patients receiving aheart transplant each year, and over 16,600 more on the waiting list fora heart, there is a persisting need for a cure or at the minimum a meansof improving the quality of life of those patients on the waiting list.

One such means of bridging the time gap while awaiting a transplant is acirculatory assist system. These systems, originally developed over adecade ago, provide assistance to the heart by way of a mechanical pump.In this way, blood is circulated throughout the vascular network despitethe diseased heart tissue. Traditionally, these circulatory assistsystems include an implantable or extracorporeal pump, a controller(internal or external), and inflow and outflow tubes connecting the pumpto the vascular network. FDA approved circulatory assist systemspartially relieve symptoms of breathlessness and fatigue associated withsevere heart failure and drastically improve quality of life.

However, the surgical process associated with the circulatory assistsystem is highly invasive. At the very least the procedure involves athoracotomy, i.e., the opening of the thoracic cavity between successiveribs to expose the internal organs. More typical is cardiac surgery,generally known as open-heart surgery, where the sternum is cut andsplit to expose the internal organs. Once the thoracic cavity isaccessed, the surgeon must enter the pleural space and puncture both thepericardium and the myocardial wall. There are great risks and anextensive recovery time associated with the invasive nature of theimplantation surgery. As such, some patients with severe symptoms arenot healthy enough for surgery to receive a circulatory assist system.

There continues to be a need for improvements in this area. For example,there is a need to provide greater accessibility to the circulatoryassist system by minimizing the invasiveness of the implantation surgeryfor those patients that would gain the most benefit while awaiting aheart transplant. Specifically, there continues to be a need to minimizethe invasiveness of the procedure by at least removing the need to enterthe pleural space or puncturing the pericardium and myocardial wall.Further, there is a need for the procedure to be easily performed withina cardiac suite or cardiac electrophysiology lab, rather than within anoperating room, so as to increase the availability to patients.

SUMMARY

In one embodiment of the present invention, a circulatory assist systemis provided. The system comprises a cannula assembly, further comprisinga cannula body for directing blood from the heart of a patient, havingdistal and proximal ends and a lumen therebetween. The cannula assemblyfurther comprises a tip coupled to the distal end of the body, the tiphaving an opening. A pump for drawing blood into the cannula assemblyand dispensing the blood from the cannula assembly and into the patientcirculatory system is provided. The lumen of the cannula body furthercomprises a first inner diameter at the proximal end and a second innerdiameter at the distal end, the first inner diameter being larger thanthe second inner diameter, and a tapered portion defined as a decreasein inner diameter from the first inner diameter to the second innerdiameter between the proximal and distal ends. The tapered portionconfigured to prevent cavitation of the blood within the cannula.

In another illustrative embodiment of the present invention, acirculatory assist system is provided. The system comprises a cannulabody having distal and proximal ends and a lumen therebetween and a pumpfor drawing blood into the cannula assembly and dispensing the bloodfrom the cannula assembly and into the patient circulatory system. Thesystem further comprises a tip at the distal end of the cannula body influid communication with the lumen and configured to communicate thelumen with a cavity of the heart. The tip includes a distal portionhaving first and second ends, having first and second diameters,respectively, the second end more distal than the first end, and thesecond diameter larger than the first diameter. The tip is configured toprevent a drop of pressure of blood entering the tip and travelingthrough the cannula.

In another illustrative embodiment of the present invention, acirculatory assist system is provided. The system comprises a cannulaassembly having distal and proximal ends and a lumen therebetween and apump for drawing blood into the cannula assembly and dispensing theblood from the cannula assembly and into the patient circulatory system.The system further comprises a delivery sheath for delivering thecannula assembly through the patient circulatory system. The deliverysheath is configured to receive the cannula assembly and move relativethereto for deploying the cannula adjacent a heart cavity and furthercomprises a distal end, a proximal end, and a body therebetween. Thebody further comprises a longitudinally disposed tensile elementembedded therein and configured to prevent deformation of the body whenthe cannula assembly moves relative to the delivery sheath.

In another illustrative embodiment of the present invention, a deliverysystem for delivering a cannula including an anchor to the heart of apatient is provided. The anchor has contracted and expanded states andthe delivery system comprises a delivery sheath, the sheath configuredto receive the cannula assembly and move relative thereto for deployingthe anchor into the expanded state. The delivery system furthercomprises a loading device configured to receive the anchor in thecontracted state and assist the delivery of the cannula into thedelivery sheath with the anchor in the contracted state. The loadingdevice further comprises a proximal end, a distal end and a lumentherebetween, the proximal end having a first inner diameter and thedistal end having a second inner diameter, the first diameter beinglarger than the second diameter. The loading device further comprises astepped portion in the lumen where the first inner diameter changes tothe second inner diameter, and a taper at the stepped portion, definedas a decrease in inner diameter between the first inner diameter and thesecond inner diameter. The taper is configured to prevent damage to theanchor when the sheath receives the cannula assembly.

In another illustrative embodiment of the present invention, acirculatory assist system for assisting the flow of blood through apatient circulatory system is provided. The system comprises a cannulaassembly for directing blood from the heart of a patient, the cannulaassembly comprising a flexible cannula body including a proximal end anda distal end and a lumen therebetween. The system further comprises apump for drawing blood into the cannula assembly and dispensing theblood from the cannula assembly and into the patient circulatory system,the pump further including an inlet and an outlet. The system furthercomprises an adaptor device between the inlet and the cannula assembly,thereby fluidicly communicating the inlet and cannula assembly. Thesystem further comprises an outflow cannula fluidicly communicating theoutlet and an artery of a patient. The inlet is disposed facing agenerally lateral direction relative to the patient.

In another illustrative embodiment of the present invention, a method ofdeploying a circulatory assist system into a circulatory system of apatient is provided. The assist system includes a cannula assembly and apump and assists the flow of blood through the circulatory system. Themethod comprises directing a cannula assembly into the circulatorysystem of a patient, wherein a distal end of the cannula assembly is influid communication with a chamber of the heart, and the body travelstherefrom to the superior vena cava and the subclavian vein, whereby thecannula assembly exits from the subclavian vein at a point thereof. Themethod further comprises fluidicly communicating an outlet of the pumpwith an artery with an outflow cannula therebetween, and fluidiclycommunicating the cannula assembly with an inlet of the pump with acannula adaptor therebetween, wherein the inlet is disposed facing agenerally lateral direction relative to the patient.

DETAILED DESCRIPTION OF DRAWINGS

FIGS. 1A through 1E are diagrammatic views of an exemplary method ofaccessing the septum of the human heart, shown in cross-section.

FIG. 2A is a perspective view of the anchoring guide-element.

FIG. 2B is an enlarged cross-sectional view taken along line 2B-2B ofthe coil end of the anchoring guide-element.

FIGS. 2C through 2E are perspective views of alternate embodiments ofthe anchoring feature of the anchoring guide-element.

FIG. 3 is a longitudinal cross section of a method of loading an anchordevice into the hub of the percutaneous transseptal sheath.

FIGS. 4A through 4D are diagrammatic views of a method of stabilizingthe fiber of the anchoring guide-element, extending through a superiorincision site.

FIG. 5 is a diagrammatic view of an exemplary method of implanting thetransseptal cannula assembly in a human heart, shown in cross-section.

FIG. 6 is a side elevational view of the delivery apparatus with thetransseptal cannula assembly, shown in partial cross-section.

FIG. 6A is a cross-sectional view of an alternative catheter shaftsimilar to the one shown in FIG. 6.

FIG. 7A is a perspective view of one embodiment of the tip of thetransseptal cannula assembly.

FIG. 7B is a transverse cross section of a transseptal cannulaembodiment where the anchor tips of right and left anchors are alignedwith one another.

FIG. 8A is a perspective view of one embodiment of an anchor used inconjunction with tip shown in FIG. 7A.

FIG. 8B is a front elevation view of another embodiment of the anchorpartially cut away.

FIG. 8C is a side elevation view of the anchor illustrated in FIG. 8B.

FIG. 8D is a front elevation view of the first and second anchors shownin the deployed state and mounted on the cannula tip of FIG. 7A.

FIG. 8E is a side elevation view of the first and second anchors shownin the deployed state without the septum shown, taken along line 8E-8Eof FIG. 8D.

FIG. 9A is a disassembled perspective view of the distal loadingapparatus in partial cross-section.

FIG. 9B is an assembled cross-sectional view of the distal loadingapparatus of FIG. 9A, in partial cross-section.

FIGS. 10A through 10D illustrate the transseptal cannula assembly beingloaded into the delivery apparatus by the distal loading apparatus,shown in partial cross-section.

FIG. 11A is a perspective view of an alternate embodiment of thedelivery device.

FIG. 11B is a longitudinal cross-sectional view of a portion of thedelivery device illustrated in FIG. 11A showing the loading of atransseptal cannula assembly.

FIGS. 12A through 12D are side elevational views in partial crosssection of an exemplary method of deploying the anchors of thetransseptal cannula assembly.

FIG. 13 is a diagrammatic view of an illustrative circulatory assistsystem positioned in the human heart shown in cross-section.

FIG. 14 is a side elevation view of another embodiment of the tip of thetransseptal cannula assembly according to another embodiment.

FIG. 15 is a disassembled perspective view of an alternate embodiment ofthe transseptal cannula assembly.

FIG. 16A is a disassembled perspective view of yet another alternativeembodiment of the transseptal cannula assembly.

FIG. 16B is a longitudinal cross-section of the transseptal cannulaassembly of FIG. 16A along the line 16B-16B.

FIG. 17 is a side elevation view, in partial cross-section, of analternate embodiment of the delivery device.

FIG. 18A is a side elevation view of the distal portion of anotherembodiment of the delivery device having a truncated sheath.

FIG. 18B is a side elevation view of the distal portion of theembodiment of FIG. 18A with the truncated sheath being retracted andbefore deployment of a first anchor.

FIG. 19A is a perspective view of one embodiment of the cannulaassembly.

FIG. 19B is a longitudinal cross-sectional view of the cannula assemblyof FIG. 19A.

FIG. 20 is a detailed cross-sectional view of the cannula assembly ofFIG. 19A.

FIG. 21A is a perspective view of one embodiment of a delivery sheath.

FIG. 21B is a detailed perspective view of the delivery sheath of FIG.21A.

FIG. 21C is a detailed cross-sectional view of the hub of the deliverysheath of FIG. 21A.

FIGS. 22A through 22D show side cross-sectional views of the stepsinvolved in loading the cannula assembly into a loading device.

FIG. 22E is a detailed cross-sectional view showing the loading devicewith the cannula assembly as shown in FIG. 22D as directed into the hubof FIG. 21C.

FIG. 23A is a diagrammatic view of an exemplary method of accessing theseptum of the human heart, shown in cross-section.

FIG. 23B is a diagrammatic view of an exemplary method of accessing theseptum of the human heart, shown in cross-section, showing a cannulaadaptor and alternative configuration of a blood pump.

FIG. 23C is a detailed side view of the cannula adaptor shown in FIG.23B.

FIG. 23D is a side view of the cannula adaptor of FIG. 23B coupled withthe cannula body.

DETAIL DESCRIPTION

Implanting a circulatory assist system can begin with a percutaneoustransseptal crossing procedure. FIGS. 1A-1E illustrate a portion of theprocedure according to one embodiment that involves the placement of ananchoring guide-element across the intra-atrial septum 102 of the heart104. The method begins with the surgeon making a primary incision site106 in the patient 108 that is substantially near a superficial vein. Asuitable superficial vein for the primary incision site 106 can includea peripheral vein, on either of the right or left sides of the patient,such as the left or right femoral veins 109, 110, or others known by oneskilled in the art. It is generally preferred that the primary incisionsite 106 is inferior to a secondary incision site 111, that issubstantially near a suitable superficial vein, including peripheralveins such as the right subclavian vein 112, the jugular vein 113, atthe junction between the right subclavian vein 112 and the jugular vein113, or other suitable peripheral veins known by one skilled in the art.Similar veins or locations on the left side of the body could also beused.

The use of an inferior incision site is better suited for accessing theleft atrium and the intra-atrial septum due to the angle of the heartand the septum with respect to the inferior and superior vena cava. Yet,some procedures, such as the implantation of a circulatory assistsystem, necessitate a more superiorly located incision site. As aresult, the surgeon may find it beneficial to first access the septumand then transition to the secondary incision site, as will be describedin detail.

The surgeon can begin the procedure as shown in FIG. 1A, by directing astandard snare device 114 from the secondary incision site 111, down thesuperior vena cava 116, the right atrium 117, the inferior vena cava118, to the right femoral vein 110, and through the primary incisionsite 106. The standard snare device 114 can include a body 120 extendingbetween the primary and secondary incision sites 106, 111 and a snareloop 121 upon the distal end of the body 120. Alternatively, snare loop121 can remain within the right femoral vein 110 and not extend throughthe primary incision site 106, though this is not shown.

The surgeon may then access and cross the intra-atrial septum 102. Asuitable device utilized for percutaneous transseptal crossing can be atransseptal access delivery system 122 having a percutaneous transseptalsheath 124 with a distal end 125, a proximal end 126, a lumen (notshown) extending therebetween, and a proximally located hub 128 upon theproximal end 126 of the percutaneous transseptal sheath 124. The distalend 125 of the percutaneous transseptal sheath 124 is directed throughthe snare loop 121, into the primary incision site 106, up the inferiorvena cava 118, and into the right atrium 117.

Once the percutaneous transseptal sheath 124 enters the right atrium117, a transseptal needle (not shown) with a guidewire 130 extendingtherethrough are back-loaded into the proximally located hub 128,through the lumen of the percutaneous transseptal sheath 124, and intothe right atrium 117. The transseptal needle (not shown) punctures theintra-atrial septum 102 and allows the guidewire 130 to enter the leftatrium 132. The distal end 125 of the percutaneous transseptal sheath124 is advanced over the transseptal needle, through the puncture withinthe intra-atrial septum 102, and into the left atrium 132. Thisadvancement of the percutaneous transseptal sheath 124 can be enabled bythe use of an obturator 134; however, the method should not beconsidered so limited.

After the distal end 125 of the percutaneous transseptal sheath 124 iswithin the left atrium 132, the transseptal needle (not shown) and theguidewire 130 are retracted completely (see FIG. 1B) leaving only thepercutaneous transseptal sheath 124 within the left atrium 132. Thetransseptal access delivery system 122 is now ready to receive ananchoring guide-element according to one of the embodiments herein andexplained in detail below.

Generally, the anchoring guide-element includes a body portion having aproximal end and a distal end, wherein the distal end includes ananchoring portion. Additional features may be included and are providedin detail below.

As shown in FIGS. 2A and 2B, the body portion of the anchoringguide-element can be constructed as a wire 138 having an internal corewire 140 can be encased within a coil 142 and/or a polymeric jacket (notshown). The core wire 140 is constructed from a superelastic material(such as Nitinol, i.e. NiTi) and will range in diameter fromapproximately 0.127 mm to approximately 0.254 mm over the length of thewire 138. The core wire 140 can be tapered or stepped, depending on thedesired level of flexibility (i.e. greater taper would increase theflexibility). The coil 142 can be constructed from a tight pitch coil ofa metallic material, such as stainless steel or platinum, and caninclude a round or rectangular cross section, with an effective diameterranging from approximately 0.0254 mm to approximately 0.127 mm.Typically, the entire length of the wire 138 can range fromapproximately 30 cm to approximately 300 cm, which will depend upon thedistance between the heart and the incision site. This constructionprovides a flexibility that aids the surgeon in maneuvering theanchoring guide-element through the percutaneous transseptal sheath, aswill be discussed below.

The coil 142 and the core wire 140 can be joined at the proximal end 144in accordance with FIG. 2B, by an end radius 145, which can be formed byadjoining the coil 142 and the core wire 140 by a laser solderingprocess, a welding technique, or other known methods. After the coil 142and the core wire 140 are adjoined, the wire 138 can then be coated witha polymeric material (not shown), such as a polyethylene or afluorinated polymer, which will improve the movement of the wire 138with respect to surgical devices directed coaxially over the wire 138.

Returning again to FIG. 2A, a distal end 146 of the wire 138 isillustrated as a straight portion, which can be an extension of the corewire material. The distal end 146 provides a stiff region that may bepre-formed as necessary to provide support to coaxially loaded devicesas well as a transition between the body portion and an anchoringportion, which is described below. The distal end 146 ranges in lengthfrom approximately 1 cm to approximately 10 cm, as is necessary ordesired.

The anchoring guide-element includes an anchoring portion upon thedistal end of the body portion. While the anchoring portion can includeany number of configurations, three are specifically described herein: adouble bend 160 (FIG. 2A), a plurality of struts 150 (FIGS. 2C and 2D),and a loop 162 (FIG. 2E).

The double bend 160 of FIG. 2A can include first and second curvedportions 164, 166 positioned at the distal end 146 of the wire 138. Thefirst and second curved portions 164, 166 can be opposed, i.e.positioned substantially 180° apart, to optimize load-bearing benefitsonce it is positioned against the septum (not shown). An end portion 168can extend proximally from the location of the double bend 160. Thedistal end 146 of the wire 138 is affixed to a proximal end 170 of thedouble bend 160 by a standard joining process such as welding or gluing.If desired, a thin polymeric sleeve (not shown) can be included tosecure the end portion 168 to the proximal end 170.

The double bend 160 of FIG. 2A can be formed at the distal end 146 ofthe wire 138 by a secondary forming process of the core wire material,which is an extension of the body portion. Alternatively, the doublebend 160 can be constructed separately, from like materials, and thenthe proximal end 170 of the double bend 160 can be attached to thedistal end 146 of the wire 138 by welding or gluing.

In FIG. 2C, the anchoring portion is illustrated as the plurality ofstruts 150. Generally, the plurality of struts 150 extend substantiallytransverse to a central axis, which is represented by the body portion(illustrated as a fiber 148 that will be discussed below). While fourstruts 150 are shown, this number is not so limited. Rather, embodimentscould be envisioned where two struts 150 or up to six or eight struts150 may be necessitated for a particular surgeon's needs or preference.To soften the wire stock materials, coils (not shown) can be added tothe distal portion of each strut 150. Alternatively, the struts 150 canbe dip-coated with a polymer. Each of the plurality of struts 150 can beconstructed into a desired shape from a flat sheet stock of superelasticmaterial, such as NiTl or MP35N. The superelastic material allows eachof the plurality of struts 150 to be folded and/or held in a positionthat is parallel to the central axis, although a parallel position isnot shown in the figure. Once released, the plurality of struts 150 willautomatically spring to a deployed state (FIG. 2C), where the deployedstate is transverse to the central axis. Alternatively, each of theplurality of struts 150 are constructed from a wire stock of the desiredmaterial and formed into the desired shape. Each of the plurality ofstruts 150 can range in thickness from approximately 0.13 mm toapproximately 0.25 mm, and in length from approximately 0.025 mm toapproximately 0.51 mm. After formation, each of the plurality of struts150 can undergo a secondary process, such as electropolishing, to removerough edges generated when forming the desired curvature.

As further illustrated in FIG. 2C, the plurality of struts 150 areattached to a fiber 148. The fiber 148 can be made from a standardsuture material, such as a polypropylene (for example etchedpolytetrafluoroethylene; ePTFE). Because the fiber 148 lacks a level ofrigidity suitable to serve as a guidewire, an anchor magnet 152 isincluded to provide a means for attaching a reinforcement structure overthe fiber 148, which will be discussed in detail below. The outerdiameter of the anchor magnet 152 is approximately equal to the diameterof a conventional guidewire (i.e. approximately 0.127 mm toapproximately 6.35 mm, generally) and has an overall length such thatthe proximal end 154 of the anchor magnet 152 will reside within theright atrium 117 (FIG. 1A) while the plurality of struts 150 (or otheranchoring portion) resides within the left atrium 132 (FIG. 1A) andalong the intra-atrial septum 102 (FIG. 1A). Generally, an anchor magnetlength ranging from approximately 1 mm to approximately 5 mm issufficient to accommodate a variety of septal thicknesses. The fiber 148extends through an inner diameter (not shown) of the anchor magnet 152and through a central portion 155 of the plurality of struts 150. Thefiber 148 is secured at the distal end 156 by welding or other means.

FIG. 2D illustrates an alternative embodiment in which a flexible wire157, constructed from NiTi, for example, is welded to a hub 158constructed, for example, of a radiopaque material for localization. Theflexible wire 157 can be solution dipped or include TEFLON or otherpolymer layer that is suitable to lower the frictional coefficient. Theproximal end (not shown) of the flexible wire 157 can be similar inconstruction to the coil 142 and core wire 140 of FIG. 2B. The pluralityof struts 150 that extend substantially transverse to a centrallongitudinal axis are welded onto the hub 158. Though not specificallyshown, each of the plurality of struts 150 can include a spring coil andan end radius upon each distal end, constructed similar to the body ofFIG. 2B. Further, each of the plurality of struts 150 can include acurvature such that the outer end of each of the plurality of struts 150is positioned more proximally than the inner end located near the hub.

FIG. 2E illustrates a third embodiment of the anchoring portion, namelythe loop 162 having a distal end portion 172 and a proximal end (notshown). Formation of the loop 162 can be by heat treatment processing.The end portion 172 of the loop 162 can be a core and coil assembly thatis similar in construction and materials to the wire of FIG. 2A toprovide increased rigidity to the end portion 172, which aids thesurgeon in maneuvering the apparatus. Herein, the end portion 172 canrange in length from approximately 1 cm to approximately 5 cm dependingupon the desired shape of the loop 162. That is, if a “straight” shapeis desired, then a length of approximately 1 cm may be appropriate;however, “j” or other shapes may require at least 5 cm.

The anchoring portion, regardless of the embodiment employed, mayfurther include a portion constructed from platinum or platinum-iridiumstainless steel so as to change the radiopacity of the anchoringportion. Radiopaque materials, such as platinum-iridium, stainlesssteel, tungsten, or tantalum, allow for remote visualization of a devicein vivo, by non-invasive devices such as X-ray, real-time fluoroscopy,or intracardiac echocardiograph.

With the details of illustrative anchoring guide-elements described withsome detail, the method of inserting the anchoring guide-element cancontinue with reference made to FIGS. 1B-1D. While these figuresillustrate the anchoring guide-element particularly as the fiber 148with the plurality of struts 150, it would be understood that otherembodiments, such as any of the embodiments described above for the bodyportion and/or anchoring portion would be appropriate.

FIG. 1B illustrates the plurality of struts 150 back-loaded into the hub128 via a loading tube 174. The loading tube 174 (see FIG. 2 for greaterdetail) will cause the plurality of struts 150 to be deflected from anexpanded state (shown in phantom) and into a position that issubstantially parallel to a central axis (as was described previously).The loading tube 174 can also act as a mechanism for opening ahemostatic valve (shown as an O-ring 175) within the hub 128. Inoperation, the plurality of struts 150 are positioned at a proximal endof the loading tube 174. By advancing the plurality of struts 150 intothe loading tube 174 while maintaining the loading tube 174 stationary,the plurality of struts 150 are deflected such that the anchoringportion is deflected and enters the loading tube 174. If necessary, dueto the non-rigid character of the fiber 148, advancing the struts 150can be accomplished by a pusher tube 176. Accordingly, a distal end ofthe pusher tube 176 contacts the anchor magnet 152 and thereby directsthe plurality of struts 150 into the loading tube 174 and thepercutaneous transseptal sheath 124 (FIG. 1B), and eventually into theleft atrium 132 (FIG. 1B) as described below. In construction, thepusher tube can be a hollow cylindrical structure that allows the fiber148 to extend therethrough. In some instances, the pusher tube 176 canbe constructed as a solid cylindrical structure of either a polymeric ora metallic material as in FIG. 1B.

In operation, and as will be appreciated by reviewing FIGS. 1B and 1C,the plurality of struts 150 are advanced through the lumen of thepercutaneous transseptal sheath 124 by the pusher tube 176 until theplurality of struts 150 emerge from the distal end 125 of thepercutaneous transseptal sheath 124 and thereby enter the left atrium132. Continued advancement with the pusher tube 176 extends theplurality of struts 150 beyond the percutaneous transseptal sheath 124causing each of the plurality of struts 150 to be deployed from theposition parallel to the central axis to the position transverse to thecentral axis (as described previously).

As illustrated in FIG. 1C, once the plurality of struts 150 are deployedwithin the left atrium 132, the surgeon can then retract thepercutaneous transseptal sheath 124 and the pusher tube 176 from theprimary incision site 106 leaving the plurality of struts 150 inposition within the left atrium 132, which is shown in FIG. 1D. A slightretraction or pulling of the proximal end (not shown) of the fiber 148pulls the plurality of struts 150 within the left atrium 132 intocontact with the intra-atrial septum 102 within the left atrium 132while the fiber 148 extends from the primary incision site 106 andthrough the snare loop 121. The snare loop 121 is then operable totransition, or move, the fiber 148 from the primary incision site 106 tothe secondary incision site 111.

FIG. 1E shows the snare loop 121 as the surgeon begins retracting thesnare device 114 and transitioning the fiber 148 from the primaryincision site 106 to the secondary incision site 111. The plurality ofstruts 150 are secured to the intra-atrial septum 102 within the leftatrium 132 and will resist the removal of the anchoring guide-elementfrom the intra-atrial septum 102. By retracting of the snare device 114,a prolapsed portion 190 of the fiber 148 is formed while the proximalend 180 extends beyond the primary incision site 106. In someembodiments, the snare loop 121 can be locked about the proximal end 180of the fiber 148.

FIG. 1E illustrates the snare device 114 after continuing theretraction, which results in the snare loop 121 (in phantom) and a loopportion of the fiber 148 (in phantom) extending externally from thesecondary incision site 111. The proximal end 180 of the fiber 148extends beyond the primary incision site 106. The loop portion of thefiber 148 will have a first side 191 a that extends from the loopportion to the anchoring portion and a second side 191 b that extendsfrom the loop portion to the proximal end 180 of the fiber. The surgeoncan then slightly pull on the first and/or second sides 191 a, 191 b ofthe loop portion of the fiber 148 to determine which extends to theanchor portion. That is, when the second side 191 b is pulled, movementis visually detected at the proximal end 180; otherwise, if the firstside 191 a is pulled, then no movement is detected. In this way, thesurgeon does not inadvertently apply too much force to the first side191 a, thereby causing the anchoring portion to pull through theintra-atrial septum 102.

With the proximal end of the anchoring guide-element extending from thesecondary incision site, subsequent percutaneous transseptal procedurescan ensue. However, as noted previously, the fiber 148 may not provide asufficient level of rigidity to support the positioning of surgicaldevices coaxially over the fiber 148. Thus, it may be necessary toincrease the rigidity of the fiber 148 by way of a reinforcementstructure, such as an over-wire assembly, described below.

FIG. 4A shows an over-wire assembly 192 to increase the strength of theanchoring guide-element. The over-wire assembly 192 includes a body 194having a distally located magnet 196. The body 194 will be positionedover the fiber 148 to provide increased rigidity. The body 194 can beconstructed of either a polymeric (e.g. polyimide or polyamide) ormetallic (e.g. stainless steel or NiTi) material. When a polymericmaterial is used, the outer surface of the polymeric material mayfurther be coated with material that reduces the frictional coefficientof the surface, such as a lubricious coating. When a metallic materialis used, the body 194 may be a continuous coil made from either round orflat wire, or may be a hypotube having helical laser cuts directedtoward the distal end of the body 194.

The magnet 196 is operable to attach the body 194 of the over-wireassembly 192 to the anchor magnet 152 at the plurality of struts 150.Thus, the magnet 196 is made of a material that is similar to the anchormagnet 152, described previously, but with an opposing magnetic polarityto facilitate coupling of the anchor magnet 152 to the magnet 196. Themagnet 196 can be affixed to the distal end of the body 194 by welding,or glue, or other suitable means.

Further illustrated in FIG. 4A is a fiber capturing device 198 includinga wire 199, a proximally positioned hub 200, and a distally positionedloop 202 for use in association with the over-wire assembly 192. Inoperation, the loop 202 can act as a needle for threading the fiber 148through the body 194, but this method will be described in greaterdetail below. The wire 199 and loop 202 can be comprised of a wirematerial, similar to the materials of a standard snare device. The hub200 can be any number of structures that provide a handle to the fibercapturing device 198 and to ensure that the proximal end of the fibercapturing device 198 does not enter the body 194. The wire 199 and loop202 can be preloaded into the body 194 such that the loop 202 extendsbeyond the magnet 196 as illustrated.

In operation and according to FIGS. 4A and 4B, the proximal end 180 ofthe fiber 148, while extending from the secondary incision site 182, isthreaded through the loop 202 of the fiber capturing device 198. The hub200 of the fiber capturing device 198 is then pulled away from the body194, thereby pulling the loop 202, along with the fiber 148, through thelumen of the body 194, as shown in FIG. 4B. The fiber capturing device198 is then fully removed from the body 194 such that the fiber 148extends proximally from the body 194.

Continuing now to FIG. 4C, the body 194 can then be advanced over thefiber 148 while the surgeon maintains tension on the fiber 148 and theplurality of struts 150 within the left atrium 132. As the body 194 andthe magnet 196 approach the intra-atrial septum 102, the magnet 196 andthe anchor magnet 152 will magnetically couple to form a continuousplatform that is stable for advancing additional devices to, and across,the over-wire assembly 192. In other embodiments, the anchor magnet 152can further include a lead-in feature (not shown), which acts as a stepfor ensuring proper alignment and coupling of the anchor magnet 152 andthe magnet 196.

To finalize the over-wire assembly 192 as illustrated in FIG. 4C, aone-way fiber clip 204 is directed over the proximal end 180 of thefiber 148 to prevent the proximal end 180 of the fiber 148 fromreentering the body 194 of the over-wire assembly 192 and to ensure thattension is maintained between the anchor magnet 152 and the magnet 196,i.e. along the fiber 148. Once the fiber clip 204 contacts the body 194,the fiber clip 204 is clamped shut and the proximal end 180 of the fiber148 extending proximally from the fiber clip 204 is trimmed.

Then, as shown in FIG. 4D, the body 194 with the fiber clip 204 in placeis ready to coaxially receive any suitable surgical apparatus. Forexample, a transseptal cannula apparatus is positioned coaxially overthe fiber clip 204 and can follow the body 194 into the secondaryincision site 182, down the right subclavian vein 112, the superior venacava 116, and into the right atrium 117 of the heart 104.

While the method of directing the anchoring guide-element has beendescribed and illustrated with some detail using a fiber, it would bereadily understood that a wire could also be used. Likewise, while themethod has been described and illustrated with some detail using theplurality of struts, it would be readily understood that a loop, doublebend, or other anchoring portion could be deployed instead.

Though not specifically shown, it is possible for the surgeon tocontinue a surgical procedure from the primary incision site withouttransitioning the anchoring guide-element from the primary incision siteto the secondary incision site. In this way, the snare device would notbe used.

It is further possible for the surgeon to directly access theintra-atrial septum from a single incision site without creating theprimary and secondary incision sites and utilizing the snare device. Inthis way, a single incision site is located substantially near thesecondary incision site, which has been described above. The surgeon candirect a standard guidewire, obturator, and a steerable sheath into thesingle incision site. By using the steering wires of the steerablesheath, the surgeon can direct the assembly through the right subclavianvein, the superior vena cava, and into the right atrium. Upon reachingthe right atrium, the surgeon directs the standard guidewire across theseptum and into the left atrium.

Finally, in some situations the surgeon may desire exchanging theanchoring guide-element with a standard guidewire before proceeding inthe surgery rather than using a reinforcement structure, such as theover-wire assembly. In that regard, the surgeon would therefore insert asheath through the secondary incision site, down to the right atrium,across the septum, and into the left atrium. By pulling on the bodyportion of the anchoring guide-element while holding the sheathstationary, the surgeon can cause the anchoring portion to be contractedinto the lumen of the sheath. Continued pulling of the body portion willretract the anchoring guide-element from the secondary incision sitewhile the sheath is held in place within the left atrium. The surgeonmay then insert a standard guidewire through the sheath and to the leftatrium. After confirming that the guidewire is within the left atrium,the surgeon can retract the sheath from the secondary incision site.

After gaining access to the septum, the procedure for implanting atransseptal cannula assembly for the circulatory assist system canproceed in accordance with the method shown in FIG. 5 illustrating theanchoring guide-element as the loop 162 and wire 138. However, it wouldbe understood that any of the anchoring guide-element embodimentsdescribed previously could be used.

As is shown in FIG. 5, a transseptal cannula assembly (not shown), byway of a delivery device 208, is loaded coaxially over the wire 138,into the secondary incision site 111, through the right subclavian vein112, the superior vena cava 116, and into the right atrium 117. Thedelivery device 208 is operable to deliver the transseptal cannulaassembly contained inside a delivery sheath 210, described in detailbelow, along the wire 138 and to the intra-atrial septum 102.

The delivery device 208 as shown in FIG. 5, and with greater detail inFIG. 6, includes the delivery sheath 210 and a hub 212 coupled with theproximal end of the delivery sheath 210. The delivery sheath 210 ispreferably constructed as three thin-layer walls, though it isillustrated as a single-walled structure in FIG. 6. An exterior layercan be constructed of polyurethane, Nylon-11, Nylon-12, or PEBAX; aninterior layer can be a liner made from an ePTFE, urethane, or Nylonwith hydrogel coating; a mid-layer can be constructed from a braidedmaterial, such as stainless steel wire, Nitinol, orpolyetheretherketones (PEEK) fibers to provide structural stability tothe delivery sheath. The interior layer or an interior liner may beextruded and placed upon a mandrel with the mid-layer and the exteriorlayer respectively formed or otherwise placed over the interior layer.Polyurethane is then placed over the entire assembly and heat shrinkwrapped over the tube for stability. Alternatively, the delivery sheath210 can be laminated by a reflow process. In some instances, asuperelastic coil 214 can be included around the delivery sheath 210 toincrease the rigidity of the delivery sheath 210. Alternatively, ametallic braid (not shown) could be included around the delivery sheath210. A polymeric layer 215 can surround the superelastic coil 214 toreduce friction as the delivery sheath 210 moves within the vascularnetwork. It would also be permissible for the delivery device 208 toinclude a lubricious material, such as HYDROMED or a polyamide, toreduce friction as the transseptal cannula assembly moves within thedelivery device 208.

The hub 212 is attached to the proximal end of the delivery sheath 210by gluing, welding, or other means. The hub 212 generally includes ameans for attaching to a Y-shaped connector 216. The Y-shaped connector216 is operable for receiving other surgical instruments through a mainport 218, such as a balloon catheter (see below), while preventing theback-flow of bodily fluid during the surgical procedure. A side port 220permits limited fluidic access via a valve 222 (FIG. 5). Though notshown, the hub 212 can attach to any suitable hemostatic seal forpreventing the back-flow of bodily fluid and should not be limited tothe Y-shaped connector illustrated.

Continuing now to FIG. 6 for greater detail of the delivery device 208and the transseptal cannula assembly 224, the delivery device 208delivers the transseptal cannula assembly 224 across the intra-atrialseptum for later operation with the circulatory assist system. Thetransseptal cannula assembly 224 includes a flexible cannula body 226, atip 228 coupled to the distal portion of the flexible cannula body 226,and first and second anchors 230, 232 coupled to the tip 228. Eachanchor 230, 232 is comprised of a plurality of struts 234. Asillustrated, the second anchor 232 is further comprised of a porouspolymeric structure 236 over the struts 234. The complete transseptalcannula assembly 224, once properly implanted, will create a shunt foroxygenated blood to flow from the left atrium of the heart to animplantable pump, and the vascular network beyond.

In constructing the transseptal cannula assembly 224, the walls of theflexible cannula body 226 are preferably designed from a biodurable, lowdurometer thermoplastic or thermoset elastomer material. Specifically,this may include an extruded aliphatic, polycarbonate basedpolyurethane; aliphatic polyether polyurethane; aromatic polyetherpolyurethane; aromatic polycarbonate based polyurethane; siliconemodified polyurethane; or silicone. Antimicrobial agents may be embeddedwithin the flexible cannula body material prior to the forming processto effectively reduce or eliminate the presence of bio-film and reducethe potential for infection. Alternatively, the antimicrobial agent maybe applied to the surface of the flexible cannula body 226 after themolding process is complete. Further, the flexible cannula body 226 canbe constructed as multiple layers, though this is not specificallyshown.

Once the flexible cannula body 226 is properly formed, it is cut to thedesired length. The proximal and distal portions 227, 229 can be formedto be about twice the thickness of the remainder of the flexible cannulabody 226, which can assist in coupling the flexible cannula body 226 tothe pump of the circulatory assist device and the tip 228, respectively.Other thicknesses for the proximal and distal portions can also be usedand are limited to the inner diameter of the delivery sheath 210. Thethicker proximal portion 227 of the flexible cannula body 226 canfurther aid in closing the space between the flexible cannula body 226and the delivery sheath 210 so that when a balloon catheter isback-loaded, the balloon catheter cannot move to the space between thedelivery sheath 210 and the flexible cannula body 226. Alternatively,the proximal and distal portions 227, 229 can be flared for coupling theflexible cannula body 226 to a pump of the circulatory assist device andthe tip 228, respectively.

In some embodiments, a lubricious coating or layer can be included onthe exterior of the flexible cannula body 226. Such a lubricious layerwould aid in the movement of the flexible cannula body 226 with respectto a delivery device 208. Suitable materials for the layer can includeePTFE, fluorinated ethylene propylene (FEP), ethylene vinyl acetate(EVA), polyvinylidene difluoride (PVDF), high density polyethylene(HDPE), PEBAX, or polyamide materials coated with a lubricious coatingsimilar to HYDROMED.

Referring again to FIG. 6, a balloon catheter 238 is illustrated for usein conjunction with the delivery device 208 when implanting thetransseptal cannula assembly 224. The balloon catheter 238 for use inthis method would include a balloon 240 constructed of a compliant tonon-compliant material, including Nylon-11, Nylon-12, polyurethane,polybutylene terephthalate (PBT), PEBAX, or polyethylene terephthalate(PET). The balloon 240 is coupled to the distal portion of a cathetershaft 242, which can be constructed of the same or a different materialas the balloon 240. Coupling of the balloon 240 to the catheter shaft242 can be by thermal bonding, adhesives, solvent, or covalent bonding.A Y-connector valve 244 can be included upon the proximal portion of thecatheter shaft 242 with a strain relief 246 for transitioning betweenthe rigid Y-connector valve 244 to the flexible catheter shaft 242. TheY-connector valve 244 can include a main port 248 and a side port 250,wherein the side port 250 can include a stop cock (not shown) forinflating or deflating the balloon 240. A marker band 251 can beincluded upon the distal end of the catheter shaft 242 for providing invivo location and alignment of the balloon 240.

In some embodiments, such as the alternate cross-section shown in FIG.6A, the balloon catheter shaft 242 a can further include at least onelumen 252 containing at least one steering wire 253 for steering theballoon 240. The at least one steering wire 253 will extend from adistal end point (not shown) within the balloon 240 (FIG. 6) through thelumen 252 and to a steering mechanism (not shown) that is attached tothe y-connector valve 244. The steering mechanism will include a slide(not shown) operable for pulling on the steering wire and thereby causethe distal end of the balloon 240 to be laterally deflected. Oncereleased, the balloon 240 will return to the undeflected position. Theballoon catheter 238 will also include an inflation lumen 255 forpassing a fluid for inflating or deflating the balloon 240.

Turning now to FIG. 7A, the tip 228 of the transseptal cannula assemblyis illustrated and described with greater detail. Generally, the tip 228includes a proximal portion 228 a, a medial portion 228 b, and a distalportion 228 c. An opening 254 extends through the proximal, medial, anddistal portions 228 a-c and provides fluidic communication between theleft atrium and the flexible cannula body 226 (FIG. 6). In a preferredembodiment, the proximal, medial, and distal portions 228 a-c areconstructed from titanium alloy, such as TiAl 6Va EL 1, by standardturning, wire electrical discharge machining (EDM), or other machiningprocesses. In this regard, and as shown most clearly in thecross-sectional view of FIG. 7B, the tip 228 is a rigid tip 228 ofunitary construction.

As further shown in FIG. 7A, the distal portion 228 c of the tip 228 caninclude a shape that will reduce fluidic drag, but the tip 228 shouldnot be considered to be limited to the shape specifically shown.Likewise, the proximal portion 228 a may be shaped according to fluidicneeds and the means of coupling the flexible cannula body to the tip228.

Continuing with FIGS. 7A and 7B, the tip 228 can further include one ormore rings 256, provided for several reasons. These rings 256 may act ina manner as to engage the anchors 230, 232 (see FIG. 7B). In this way,rings 256 may act in conjunction with clamps 258 (FIG. 7B) to affix theanchors 230, 232 upon the tip 228. Further, the rings could be used toseat the anchors 230, 232 and can be keyed in a way so as to maintain anorientation of the anchor. Suitable clamps 258 may includeconfigurations as shown or others such as, but not limited to, swage orcrimp-style clamps. The clamps 258 could alternately be attached to thetip 228 by an adhesive, welding, or tying. The tip 228 may furtherinclude one or more barbs 260 upon the proximal end 228 a of the tip228. Barbs 260 provide resistance against the undesired removal of theflexible cannula body 226 (FIG. 6) from the tip 228.

In construction, the rings 256 and barbs 260 can advantageously bemolded as a portion of the tip 228. Alternatively, the rings 256 areswaged or crimped into place after the tip 228 is constructed. In someembodiments, the rings 256 may optionally be constructed of radiopaquematerials such as to aid in localization of the transseptal cannulaassembly 224 (FIG. 6). Alternatively, a separate radiopaque band (notshown) may be constructed and placed sufficiently near the rings 256.

Turning now to FIGS. 8A-8E, the details of the anchors 230, 232 of thetransseptal cannula assembly are explained with greater detail.Specifically shown in FIG. 8A, each anchor 230, 232 includes a pluralityof struts 234 extending from a central ring portion 262. The pluralityof struts 234 and central ring portion 262 may be etched as a singleunit from the same piece of superelastic material to form internalsupport structure for each of the anchors 230, 232. Alternatively, itwould be possible to permanently affix each strut 234 to a separatelymanufactured central ring portion 262, such as by welding or othermeans. It should be appreciated that while four struts 234 are shown peranchor 230, 232, this number is not so limited. Rather, embodimentscould be envisioned where fewer or more struts 234 may be necessitatedor desired for a particular surgeon's needs or preference. Providing atleast three struts can result in greater stability of the implanted tip228 (FIG. 7B).

The struts 234 and ring portion 262 can be at least partiallyconstructed from a superelastic NiTi material by chemically etching theparts from flat sheet stock, electropolishing the etched parts to removerough edges generated during the formation process, and then heating theparts to a superelastic state. While the preferred materials arespecifically taught herein, other suitable biocompatible, non-compliant,flexible material would be sufficient for the tip or the anchors.

FIG. 8B illustrates, with some detail, the anchors 230, 232 furtherincluding the porous polymeric structure 236. In function, the porouspolymeric structure 236 provides a larger surface to engage the septum(not shown) than the plurality of struts 234 alone. Further, the porouspolymeric structure 236 allows for tissue in-growth, wherein tissue fromthe septum may grow and embed within the porous polymeric structure 236to provide greater structural stability and sealing capacity. Whileeither or both of the anchors 230, 232 can include the porous polymericstructure 236, it is generally preferred that only the second anchor232, which will reside along the septum (not shown) within the rightatrium (not shown), will include the porous polymeric structure 236.This configuration is preferred because the right atrium is larger involume than the left atrium; however, the invention should not beconsidered so limited.

Suitable materials for the porous polymeric structure 236 may include,but are not limited to, polyester monofilament or multifilament yarn;ePTFE monofilament or multifilament yarn; or fluorinated polyolefinfibers or yarns, which can be woven, braided, knitted, or felted into aproper configuration. The porous polymeric structure 236 may furtherinclude various intrinsic configurations including weaves, braids, orknits having two or three-dimensional honeycombs, circular, flat, ortri-axial tubular structures. In other embodiments, the porous polymericstructure 236 may be constructed from an ePTFE piece in tubular,cylindrical, or sheet form. Generally, the porous polymeric structure236 will be constructed by etching or laser cutting a shape from twosheets of a stock material (such as those described above). The shapedpolymeric structures 236 are then ultrasonically welded together suchthat the shaped polymeric structures capture the anchor therebetween.

As is further shown in FIG. 8B, each strut 234 can include a marker 264.The marker 264 can be constructed from a fluoroscopic paint such thatthe location of the anchor 230, 232 is visible by intracardiacechocardiography. In this way, the marker 264 enables the surgeon todifferentiate between an anchor 230, 232 that is parallel to thelengthwise central axis, represented by the wire 138, from one that istransverse to the same axis. Thus, the surgeon is capable of determiningthe state of deployment of the first and second anchors 230, 232, invivo. Other suitable materials for the marker 264 may include radiopaqueor similar materials.

FIG. 8C shows the deployed anchors 230, 232 in a side elevation view.The plurality of struts 234 cause the anchors 230, 232 to have a slightconcave curvature. Because the actual size, shape, and structure of theheart and intra-atrial septum may change from patient-to-patient, thisslight concave curve, which is directed toward the septum, permits asingle transseptal cannula assembly design to be adaptable to a widerange of anatomies. Additionally, the slight curve provides a greaterelastic clamping action against the septum.

FIGS. 8D-8E illustrate that the anchors 230, 232 can be positioned suchthat the first anchor 230 is offset with respect to the second anchor232. This is the preferred configuration of the deployed anchors 230,232 because of the particular load-bearing benefits. However, it wouldalso be possible to include anchors with no offset if the particularneed would arise. Additionally, it is possible to construct the anchors230, 232 in a way such that the second anchor 232 is larger than thefirst anchor 230 to provide larger surface contact area, as is shown inFIG. 8E. This configuration is more desirable than the reverse becausethe right atrium is larger in volume than the left atrium; however, theinvention should not be considered so limited. For example, in someembodiments, it may be preferred to include only the first anchor 230 onthe tip 228. In this embodiment, the first anchor could include theporous polymeric structure 236, or could remain bare.

As shown in FIG. 8E, the slight concave curve can cause the first andsecond anchors 230, 232 to cross in their free-standing deployed statewhen mounted upon the tip 228 (FIG. 6).

Because the anchors are transverse to the lengthwise central axis in thenatural state, it is necessary to fold the anchors to a position that isgenerally parallel to the lengthwise central axis and suitable forloading the anchors into the delivery sheath.

FIGS. 9A and 9B illustrate a cannula loading device 266 for loading thetransseptal cannula assembly 224 into the delivery device 208 as shownin FIG. 6. The cannula loading device 266 includes a plunger 268 withina plunger housing 270. The plunger 268 includes large and small diameterportions 272, 274. The small diameter portion 274 receives a spring 276.The proximal end of the plunger 268 can include internal screw threads279 (FIG. 9B) for receiving a screw 280 and washer 282 and thus maintainthe spring 276 on the small diameter portion 274.

FIGS. 9A-9B and 10A-10D illustrate a distal end of the plunger housing270 including a plurality of slots 286 and a plurality of fingers 288.The number of slots 286 corresponds with the number of struts 234 of thefirst anchor 230; the number of fingers 288 corresponds with the numberof struts 234 of the second anchor 232. The plunger housing 270 furtherincludes interiorly located first and second steps 290, 292, wherein thefirst step 290 is located proximal to the second step 292.

In operation, and as illustrated in FIGS. 10A-10D, the transseptalcannula assembly 224, leading with the tip 228, is inserted into thedistal end 284 of the plunger housing 270 such that the struts 234 ofthe first anchor 230, align with the plurality of slots 286 and therebyremain in a deployed state as shown in FIG. 10A. As the tip 228 ispositioned further within the plunger housing 270, each strut 234 of thesecond anchor 232 will align with each of the plurality of fingers 288and the corresponding second step 292, thereby causing each strut 234 ofthe second anchor 232 to collapse into a contracted state that issmaller in diameter than the inner diameter of the delivery sheath 210.

From FIGS. 9A-9B and 10A-10D, it will be understood that the relativepositions of the first and second steps 290, 292 can aid in determiningthe depth at which the transseptal cannula assembly 224 will be insertedwithin the delivery sheath 210. For example, if the second step 292 ispositioned close to the first step 290, then a larger portion of thedelivery sheath 210 will be inserted over the second anchor 232. Theopposite would also be true. Thus, upon depressing the plunger 268, thetransseptal cannula assembly 224 will be positioned further within thedelivery sheath 210.

Referring specifically now to FIGS. 10A and 10B, once the tip 228 of thetransseptal cannula assembly 224 is fully inserted within the plungerhousing 270 (i.e. the first anchor 230 contacts the first step 290) andthe flexible cannula body 226 extends distally from the cannula loadingdevice 266, the delivery sheath 210 can be directed over the flexiblecannula body 226 and up to the second step 292. Because the secondanchor 232 is deflected (as shown) to a diameter that is smaller thanthe inner diameter of the delivery sheath 210, the delivery sheath 210can pass between the second anchor 232 and the plurality of fingers 288to make contact with the second step 292.

FIGS. 10C-10D, illustrate loading of the transseptal cannula assembly224 into the delivery sheath 210 by transferring the tip 228 from thecannula loading device 266 to the delivery sheath 210. The surgeon thenpresses against the screw 280 (FIG. 9B) of the proximal end 278 (FIG.9B) of the plunger 268, thereby depressing the spring 276 (FIG. 9B) andadvancing the large diameter portion 272 of the plunger 268 in thedirection of arrow 294. After the plunger 268 makes contact with the tip228, further pressing of the plunger 268 in the direction of arrow 294will cause the second anchor 232 to enter the delivery sheath 210 asshown in FIG. 100. Further movement of the plunger 268 will cause thetip 228 to enter the delivery sheath 210 and initiate folding of thefirst anchor 230 as in FIG. 10D.

Once the plunger 268 has reached the end of its stroke, the transseptalcannula assembly 224 will be loaded within the delivery sheath 210 suchthat the second anchor 232 is deflected and extends proximally while thefirst anchor 230 is deflected and extends distally. When the spring 276(FIG. 9B) is released, the plunger 268 will return to a rest positionand the cannula loading device 266 is removed from the transseptalcannula assembly 224 and the delivery sheath 210.

FIG. 11A illustrates an alternate delivery device 296 for use with atransseptal cannula assembly. The delivery device 296 includes adelivery sheath 298 and a proximally located hub 300, such as ahemostasis valve. The hub 300 can further include a side port 306 havinga tube 308 and a valve 310 for fluidic access. A removable loading tube302 is pressed into the proximal end of the hub 300 to open thehemostasis valve and allow an obturator 311 to extend through thedelivery sheath 298 for dilating the opening within the intra-atrialseptum created by the wire 138. The obturator 311 and loading tube 302are removed before loading the transseptal cannula assembly (not shown).Finally, a distally located marker band 313 can be used forlocalization, in vivo.

FIG. 11B illustrates the use of a proximal loading device 312 forloading of the transseptal cannula assembly 224 into the delivery device296. The proximal loading device 312 includes a tube structure 314,preferably constructed from ePTFE or FEP, and a handle 316 constructedof a stiff material to assist the surgeon in manipulating and dockingthe proximal loading device 312 with the delivery device. Suitablematerials for the handle 316 can include acrylonitrile butadiene styrene(ABS) or a polycarbonate. While not specifically shown in FIG. 11B, thehandle 316 may include a bonding ring proximate to and circumferentiallysurrounding the tube structure 314 and an access port for injecting anadhesive suitable for coupling the handle 316 to the tube structure 314.Alternative manners of adjoining the handle 316 and tube structure 314may also be used.

Continuing with FIG. 11B, the surgeon has docked the proximal loadingdevice 312 with the delivery sheath 298 (FIG. 11A) at the hub 300. Thehub 300 includes an O-ring 318 as part of the hemostasis valve capableof forming a fluid tight seal around the delivery sheath 298. Atransition point 322 between the tube structure 314 of the proximalloading device 312 and the delivery sheath 298 should be madesubstantially without interruption such that the transseptal cannulaassembly 224 moves smoothly and freely from the proximal loading device312 and into the delivery device. Transfer of the transseptal cannulaassembly 224 to the delivery device can then be accomplished by pushingthe flexible cannula body 226 in a distal direction, shown with arrow324.

Turning now to FIGS. 12A-12D, once the transseptal cannula assembly 224has been loaded into the delivery sheath 298, the surgeon back-loads theballoon catheter 238 through the proximal portion of the transseptalcannula assembly 224. The balloon catheter 238 is then positioned withinthe tip 228 such that the marker band 251 aligns with the distal end ofthe delivery sheath 298. The balloon 240 is then inflated with a fluid(FIG. 12A), which is typically saline with or without a contrast agent.When fully inflated, the distal end of the balloon 240 expands radiallybeyond the first anchor 230 and engages the inner diameter of thedelivery sheath 210 and the inner diameter of the tip 228, therebysecuring the tip 228 and the delivery sheath 210.

The balloon catheter 238, the transseptal cannula assembly 224, and thedelivery device 208, as a unit, are then positioned over the proximalend (not shown) of the wire 138 and advanced into the secondary incisionsite 182 (FIG. 5). The delivery device 208, with the transseptal cannulaassembly 224 and balloon catheter 238 will follow the wire 138 throughthe right subclavian 112 (FIG. 5), the superior vena cava 116 (FIG. 5),and into the right atrium 117 (FIG. 5).

As shown in FIG. 12A, once the delivery device 208 and the transseptalcannula assembly 224 are within the right atrium 117, the surgeon canadvance the delivery device 208 with the transseptal cannula assembly224 and balloon catheter 238, as a unit, over the wire 138 such that aproximal cone 325 of the inflated balloon 240 dilates the openingcreated by the wire 138 through the intra-atrial septum 102.

Continuing now to FIG. 12B, where the opening through the intra-atrialseptum 102 has been dilated and the delivery device 208 has beenadvanced in the direction of arrow through the dilated opening throughthe intra-atrial septum 102. Thus, the balloon 240, the first anchor230, and the distal end 228 c of the tip 228 reside within the leftatrium 132. The surgeon then deflates the balloon 240 and realignsballoon 240 with the tip 228 by aligning the marker band 251 (FIG. 12A)with markers (not shown) on the tip 228. The balloon 240 is thenre-inflated to engage the inner diameter of the tip 228 while permittingrelative movement between the tip 228 and the delivery sheath 210.

In FIG. 12B, the surgeon advances the balloon catheter 238, with the tip228 beyond the delivery sheath 210, such that the first anchor 230 ismoved beyond the delivery sheath 210 and into the left atrium 132. Inthis way, the first anchor 230 is deployed (spring outward) from thecontracted state (in phantom) to the deployed state (in solid), withinthe left atrium 132. The second anchor 232 remains in the contractedstate and within the delivery sheath 210. The balloon catheter 238 canthen be retracted, thereby retracting the tip 228 and such that thefirst anchor 230 contacts the intra-atrial septum 102.

FIG. 12C illustrates the retraction of the balloon catheter 238 alongwith the tip 228 and the delivery sheath 210 until the deployed firstanchor 230 contacts the intra-atrial septum 102 within the left atrium132.

Finally, as shown in FIG. 12D, the surgeon continues to retract thedelivery sheath 210 in the direction of the arrow while the ballooncatheter 238 and tip 228 are maintained in position. This deploys thesecond anchor 232 in a manner similar to the first anchor 230, from acontracted position, shown in solid in FIG. 12A-12C and in phantom inFIG. 12D, to an expanded position, shown in solid in FIG. 12D. Thisdeployed second anchor 232 engages the intra-atrial septum 102 withinthe right atrium 117. Together, the first and second anchors 230, 232will prevent movement of the tip from the intra-atrial septum 102.

Now that the tip 228 and the anchors 230, 232 are implanted on oppositesides of the intra-atrial septum 102, the delivery sheath 210 can thenbe removed from the secondary incision site 182 (FIG. 5). The balloon240 is again deflated and the balloon catheter 238 removed from thesecondary incision site 182 (FIG. 5). Finally, the anchoringguide-element is removed by retracting the wire 138 while maintainingthe position of the transseptal cannula assembly 224, thereby causingthe loop 162 (FIG. 5) or other anchoring portion to collapse and enterthe transseptal cannula assembly 224 in a manner that has been describedpreviously. After the anchoring guide-element has been fully removed,only the transseptal cannula assembly 224 remains in place.

In an alternate method of implanting the transseptal cannula assembly,which is not shown in the drawings, the opening through the intra-atrialseptum is pre-dilated with a removable obturator or a balloon catheterthat expands to a diameter that is approximately equal to the outerdiameter of the delivery sheath. A suitable removable obturator maycomprise a rod and an expanded portion upon the distal end of theobturator. While the obturator is preferably constructed from Nylon-11,Nylon-12, or PEBAX, other suitable materials are also appropriate. Therod can include a marker band near the expanded portion and aligned withthe delivery sheath. The marker band can be made from any material thatwould enable a surgeon to remotely determine the location of the distalend of the delivery sheath within the heart. The surgeon can advance theobturator over the guidewire and into the right atrium. Continuedadvancement of the obturator, or the distal cone of the balloon catheterdilates the opening within the intra-atrial septum. Upon retraction ofthe obturator from the secondary incision site, the opening within theseptum does not immediately recoil, but remains slightly stretched,which more easily receives the delivery sheath with the balloon catheteras described above or without the balloon catheter.

In yet another method of implanting the transseptal cannula assembly,the surgeon can include a balloon catheter in a manner different thanwas described previously. That is, the balloon catheter is insertedwithin the transseptal cannula assembly while the balloon is in adeflated position. Once the distal portion of the tip of the transseptalcannula assembly is within the left atrium and the delivery sheath isinitially being retracted, the balloon catheter is simultaneouslyinflated. The combined acts of retracting the delivery sheath whileinflating the balloon catheter will ensure proper and completedeployment of any of the anchors described herein.

After the transseptal cannula assembly has been implanted in accordancewith one of the methods described previously, and all assistant devices(i.e. the guidewires, delivery device, balloon catheters, obturators,etc.) have been removed from the secondary incision site, thecirculatory assist system can be implanted.

FIG. 13 illustrates the implanted circulatory assist system 334 inassociation with the transseptal cannula assembly 224. In that regard,the flexible cannula body 226, which generally extends from theintra-atrial septum 102 to the secondary incision site 111 (via thesuperior vena cava 116 and right subclavian vein 112), is cut to anappropriate length and attached to the input port 336 of the implantablepump 338. A separate outflow cannula 340 is attached to the output port342 of the implantable pump 338, which is then surgically attached so asto communicate with a suitable superficial artery, such as the rightsubclavian artery 344. At this time, the surgeon may position theimplantable pump 338 subcutaneously or submuscularly within thesecondary incision site 111 or maintain the pump 338 externally evenafter the secondary incision site 111 is closed.

As also shown in FIG. 13, the pump 338 is operably associated with acontroller 346, which may also be implanted or remain external to thepatient 108. A signal transmission means 348 is provided between thepump 338 and the controller 346 and may be either a hard-wired orwireless communications device. In operation, the controller 346 mayregulate the pumping action of pump 338. Additionally, a memory device350 may be included within the controller 346 that will record pumpactivity for subsequent doctor evaluation and interaction.

Alternatively, as also shown in FIG. 13, when only the first anchor onthe tip 228 is used, a hemostasis cuff 351 (shown in phantom) can act asthe second anchor and can prevent distal movement of the transseptalcannula assembly 224. The hemostasis cuff 351 provides a seal around thetransseptal cannula assembly 224 at the wall of the right subclavianvein 112. In construction, the hemostasis cuff 351 can be constructed ofan elastic material, such as collagen, that will expand upon contactwith a fluid, such as blood.

The completed flow of blood according to a preferred embodiment and asshown in FIG. 13 will be as follows: oxygenated blood will travel fromthe left atrium 132 via the natural path into the left ventricle 352 tothe aorta 354. From the aorta 354, blood moves into the left subclavianartery 356, the left common carotid 358, and the brachiocephalic trunk360. Oxygenated blood will also enter the transseptal cannula assembly224 from the left atrium 132. Blood will enter the flexible cannula body226 and travel through the lumen of the flexible cannula body 226 to thepump 338. The pump 338 actively pumps blood into the outflow cannula 340and into the right subclavian artery 344. From here, the blood isdirected into the remainder of the vascular network.

In one alternate embodiment, illustrated in FIG. 14, a tip 362 havingproximal, medial, and distal portions 362 a-c, can include an anchorconstructed to resemble screw threads 364 upon the distal portion 362 c.In this way, the surgeon would rotate the tip 362 through theintra-atrial septum (not shown) such that successive screw threads 364of the anchor will adjoin the walls of the septum. The proximal end 362a could include barbs 366 for attaching the flexible cannula body 226(FIG. 6) of the transseptal cannula assembly 224 (FIG. 6). While thisembodiment is illustrated in isolation, the tip 362 may be used with anyof the deployable anchor embodiments described herein.

FIGS. 15, 16A and 16B illustrate two versions of alternate embodimentsof the tip and the anchors. Specifically, FIG. 15 illustrates a tip 368with proximal, medial, and distal portions 386 a-c having an anchor 370formed upon the proximal end 368 a and including first and second setsof struts 372, 374 extended from a single central portion 376. Thissingle central portion 376 permits the struts 372, 374 of the anchor 370to be constructed as a double-sided unit. In this alternative, thestruts 374, which remain within the right atrium 117 (FIG. 12D), areconstructed to be larger than the struts 372. The struts 372, 374 areslender and long to increase the surface contact area between theintra-atrial septum 102 (FIG. 12D) and the struts 372, 374 withoutnecessarily including a porous polymeric structure covering the struts372, 374.

However, as shown in FIG. 15, when the benefit of the porous polymericstructure is desired but space is limited, it would be permissible toinclude a smaller ring of porous polymeric structure 378 with the tip368. This ring of porous polymeric structure 378 can act in a mannerdescribed previously, i.e. a surface for tissue in-growth but withoutincreasing the size of the anchor 370. The distal end 368 c can beshaped to include a flared portion 380 to define a mounting groove 382for receiving the ring of porous polymeric structure 378. Thus, inassembling the tip 368, the ring of porous polymeric structure 378 andsingle central portion 376 can be secured within the mounting groove 382by pressing the components together. Alternatively, the tip 368, ring ofporous polymeric structure 378, and the anchors 370 can be secured bywelding or other suitable means.

Another embodiment as shown in FIGS. 16A and 16B, is a tip 384 havingproximal, medial, and distal portions 384 a-c, and includes asingle-sided anchor 386 having a plurality of paddle-struts 388extending from a central portion 390. The paddle-struts 388 are deployedwithin the left atrium (not shown). The plurality of paddle-struts 388provides additional surface contact area between the intra-atrial septum102 (FIG. 12D) and each of the plurality of paddle-struts 388. While notdirectly shown, it would be possible to construct a double-sided anchor,similar to that of FIG. 15, but with the plurality of paddle-struts 388.Accordingly, the shapes of the struts may vary according to a particularsurgical need and need not be limited to those shown herein.

FIGS. 16A and 16B illustrate a ring of porous polymeric structure 392,similar to that described previously, but larger in surface area. Inthat regard, the distal end 384 c of the tip 384 can include an enlargedflared portion 394 to create a surface 396 and mounting groove 398 forengaging the ring of porous polymeric structure 392 and the centralportion 390 of the anchor 386. This enlarged flared portion 394 canprovide even greater stability and support to the ring of porouspolymeric structure 392. Additionally, it would also be permissible toadhere the ring of porous polymeric structure 392 to the surface 396 foreven greater stability.

FIG. 16B further illustrates the portions of the ring of porouspolymeric structure 392 between each of the plurality of paddle-struts388 that will engage the intra-atrial septum 102.

In another alternate embodiment, as shown in FIG. 17, the flexiblecannula body 400 can include first and second control wires 402, 404upon the proximal end 406. The control wires 402, 404 allow the surgeonto maintain control of the position of the flexible cannula body 400 andthus the tip 228 (FIG. 6) within the patient's heart while the deliverysheath 210 (FIG. 6) is being removed from the secondary incision site.As shown, the first and second control wires 402, 404 can be constructedfrom stainless steel and can further be braided, as shown at 408, toincrease strength and stability of the individual control wires 402,404. The overall length of control wires 402, 404 could, for example,extend the total length of the flexible cannula body 400 to at least oneand one-half times the length of the delivery sheath 210 (FIG. 6). Thiswould ensure the surgeon's control over the position of the transseptalcannula assembly at any time during the surgical procedure.

A marker band 410, also shown in FIG. 17, can be positioned near theproximal end 406 of the flexible cannula body 400 so that the positionof the flexible cannula body 400 can be monitored, in vivo. The markerband 410 can be constructed of radiopaque materials, similar to thosedescribed previously.

In other embodiments, at least a portion of the flexible cannula body400 can include a coil 412 to reinforce the molded flexible cannula body400. Materials suitable for the coil 412 may include high-elastic orsuperelastic metallics, including NiTi or spring tempered stainlesssteel wire.

In operation, as the surgeon retracts the delivery sheath, fordeployment or complete retraction from the secondary incision site, thesurgeon grasps the control wires 402, 404 of the flexible cannula body400. In this way, the position of the tip, anchors and flexible cannulabody 400 within the intra-atrial septum can be maintained while thedelivery sheath is retracted.

In yet another embodiment, the delivery device can include a sheathconstructed from a peel away material. In this way, after thetransseptal cannula assembly has been properly inserted, the sheath issplit and removed.

Finally, FIGS. 18A and 18B illustrate yet another embodiment (see alsoFIG. 4D) for aiding in the deployment of the anchors, the deliverysheath can be replaced with a truncated sheath 414, which is constructedto cover only the tip 228 (FIG. 6) and anchors (only the first anchor230 is shown) and thus does not extend the entire length of the flexiblecannula body 226. The truncated sheath 414 extends proximally by atleast one control wire 416 to the secondary incision site 111 (FIG. 1A).In this way, the surgeon is able to move the truncated sheath 414 bypulling on the control wire 416 and thus deploying the anchors in amanner similar to that described previously. The particular benefit tothis embodiment is that the surgeon can have greater control overmaintaining the position of the transseptal cannula assembly 224 thanwas permitted with the previously described delivery sheaths. Inessence, much of the length of the delivery sheath 210 has been replacedby one or more control wires 416, which more easily permits blood tocontinue flowing around the transseptal cannula assembly during theimplanting surgical procedure.

With reference to FIG. 19A-19B, an alternative embodiment of atransseptal cannula assembly 500 of a circulatory assist system isshown. The transseptal cannula assembly 500 includes a cannula body 502having a proximal end 504, a distal end 506, and a lumen 508therebetween. The cannula body 502 may include a reinforced portion 510,as shown by coils 512 disposed along the length of the cannula body 502.In an alternative embodiment, instead of having a circular cross-sectionas shown in FIG. 19A, the coils 512 may have a substantially rectangularcross-section (not shown), thereby reducing the cross-sectional area ofthe coils 512. Such a configuration of coils 512 may advantageouslyprovide for a reduction in the overall cross-sectional area of thecannula body 502.

A tip 514 is coupled to the distal end 506 of the cannula body 502 andincludes an opening 516 communicating with the lumen 508 of the cannulabody 502. More specifically, the tip 514 is coupled to the cannula body502 by an interference fit. Barbs 538 (FIG. 22) may provide resistanceagainst the undesired removal of the cannula body 502 from the tip 514.The tip 514 may also preferably include anchors 518 a, 518 b.

The lumen 508 has a first inner diameter 519 a at the proximal end 504and a second inner diameter 519 b at the distal end 506. The first innerdiameter 519 a is larger than the second inner diameter 519 b, therebydefining a tapered portion 520 in the lumen 508. The tapered portion 520is configured to prevent cavitation of the blood within the lumen 508 asthe pressure of the blood decreases from the distal end 506 to theproximal end 504 of the cannula assembly 500, as the blood is drawn froma cavity of the heart 15 and directed into the circulatory system of apatient 14 (FIGS. 23A through 23B).

More specifically, the lumen 508 includes a first inner diameter 519 aalong a proximal portion 522 of the lumen 508. Along the proximalportion 522, the first inner diameter 519 a remains constant. In oneembodiment, the first inner diameter 519 a along the proximal portion522 is about 5.75 to 5.8 mm. The tapered portion 520 in the lumen 508 isdefined as a stepped tapered portion such that at the beginning of thetapered portion 524, the inner diameter of lumen 508 is about 5.75 to5.8 mm. At an end point 526 of tapered portion 524, the inner diameterof lumen 508 is about 5 mm. Then, continuing along the distal portion528, the inner diameter of lumen 508 is about 5 mm until the distal end506 of the cannula body 502. In a preferred embodiment, cannula body 502and lumen 508 have a length of about 290 mm. In the lumen 508, proximalportion 522 has a length of about 190 mm, tapered portion 520 has alength of about 30 mm, and distal portion 528 has a length of about 70mm. In this embodiment, providing a tapered portion 520 within the lumen508 results in a 25% improvement in pressure loss as blood travels fromthe cavity of the heart at the distal end 506 of the cannula body 502 tothe proximal end 504, where the cannula body 502 communicates with thecirculatory system of a patient.

In an alternative embodiment, the lumen 508 may be provided with analternatively configured tapered portion 520. Instead of having astepped tapered portion as discussed with respect to FIG. 19A-19B, thetapered portion 520 could be defined as a constant taper between thefirst inner diameter 519 a of the proximal end 504 and the second innerdiameter 519 b of the distal end 506. Further alternatively, the lumen508 may include more than one stepped tapered portion between theproximal and distal ends 504, 506 configured to reduce pressure loss andprevent cavitation of blood traveling from the distal end 506 to theproximal end 504. Moreover, these dimensions disclosed above arespecific to the embodiment described above and are not meant to limitthe disclosure herein.

With reference to FIG. 20, it may be advantageous to provide the tip 514of the cannula assembly 500 with characteristics that improve blood flowcharacteristics of the cannula assembly 500. Tip 514 includes a proximalend 514 a, a distal end 514 b, and a body 517 therebetween. As shown inFIG. 20, distal portion 515 of tip 514 includes first and second ends530, 532 having first and second inner diameters 534 a, 534 b,respectively. The second end 532 is more distal than the first end 530and the second inner diameter 534 b is larger than the first innerdiameter 534 a. In one embodiment of the tip 514, the difference in thefirst and second inner diameters 534 a, 534 b defines at least a portionof the tip 514 as a generally campanulate, or bell-shaped, member. Morespecifically, the tip 514 includes a first end 530 with a first innerdiameter 534 a and a second end 532 with a second inner diameter 534 b.In between the first and second ends 530, 532 is a generally curvilinearportion 536, thereby defining at least a portion of the tip 514 as agenerally campanulate shape.

The campanulate shape of the tip 514 provides fluid flow benefits forthe circulatory assist system. More specifically, the campanulate shapeprovides a smoother flow transition, and thus lower pressure losses, asa fluid is moving from the larger heart chamber, into the smaller tip514 and cannula body 517. Reducing pressure losses of the fluid or bloodentering the tip 514 provides for a more advantageous circulatory assistsystem. Furthermore, advantageously, the campanulate shape reduces theoccurrence of turbulence of blood at the tip 514 and in the cannula 502when blood is drawn into the lumen 508, thereby increasing the overallefficiency and efficacy of the system.

The generally campanulate tip 514 may be free of imperfections that maycause thrombus formation. For example, the tip 514 may be polished inorder to remove any imperfections that may lead to thrombus formation.Moreover, the transition between the cannula body 502 and the tip 514may be smooth and free of irregularities that may cause thrombus.

With further reference to FIG. 20, the tip 514 may further include oneor more barbs 538 on the proximal end 514 a of the tip 514. Barbs 538provide resistance against the undesired removal of the cannula body 502from the tip 514. In addition to barbs, a swaged or crimped band 540 maybe provided on the cannula body 502 to provide further resistanceagainst the undesired removal of the cannula body 502 from the tip 514.The swaged or crimped band 540 may be comprised of a malleable material,such as tantalum, to accommodate for large fluctuations in size of thecannula body 502. Advantageously, if desired, the swaged or crimped band540 may be used as a fluoroscopic visualization marker if constructedfrom a radiopaque material, such as tantalum.

Continuing with FIG. 20, the tip 514 can further include one or morerings 539, provided for potentially several reasons. For example, theserings 539 may act in a manner as to engage the anchors 518 a, 518 b.Advantageously, the rings 539 may be provided with a porous polymerstructure 541 such as polyester fabric wherein tissue from the septummay grow and embed within the porous polymeric structure 541 to providegreater structural stability. The distal end 506 of cannula body 502 mayessentially abut one of the anchors 518. Further, additional rings 537may be included and could be used to seat the anchors 518 a, 518 b andcan be keyed in a way so as to maintain an orientation of the anchors518 a, 518 b.

FIG. 21A shows an alternative embodiment of a delivery sheath 542. Thedelivery sheath 542 further comprises a distal end 544, a proximal end546, and a body 548 therebetween. The delivery sheath 542 includes a hub543 at the proximal end 546 operably connected to tubing 545 connectableto an air source or for venting the hub 543 or delivery sheath 542. Dueto the material characteristics of the delivery sheath 542, the deliverysheath 542 tends to deform in the direction of movement of the cannulaassembly 500 as the cannula assembly 500 moves relative to the deliverysheath 542 during delivery of the cannula assembly 500 to the septum.The plastic deformation of the sheath 542 is disadvantageous whenadvancing the cannula anchors 518 out of the tip 514 because thedelivery sheath 542 may stretch as the proximal anchors 518 a exit, thensubsequently recoil in an uncontrolled manner. The sheath behaving insuch a manner may inadvertently deploy the distal anchors 518 b in theleft atrium. The tensile element 550 is used to prevent this andtherefore gives the physician precise control of the sheath tip 514 whendeploying each anchor 518 a, 518 b.

As shown in FIG. 21A, the delivery sheath 542 includes a longitudinallydisposed tensile element 550. The tensile element 550 prevents thestretching and subsequent recoil as described above, and therefore givesthe physician precise control of the sheath tip 514 when deploying eachset of anchors 518 a, 518 b. In an alternative embodiment, however, thedelivery sheath 542 could have more tensile elements 550. For example,the body 548 of the delivery sheath 542 could have at least two or moretensile elements 550, preferably equally spaced apart. The tensileelement may be flexible such that it does not compromise the bendingcharacteristics of the sheath 542. The tensile element 550 may thereforecomprise a material which is configured to provide the desired bendingcharacteristics of the sheath 542. Preferably, the tensile element 550comprises a monofilament or polyfilament of a polymeric material. Morespecifically, the tensile element may comprise a polyfilament which maycomprise wound or braided polymeric material. The tensile element 550may be embedded in the body 548 of the delivery sheath 542 such that thetensile element 550 is disposed between inner and outer walls (notshown) of the body. The tensile element 550 may be embedded in the body548 in such a manner by a variety of manufacturing methods. In oneembodiment, the tensile element is held in tension using slots in eachend of a mandrel while the sheath 542. A reflow process, usingFluorinated ethylene propylene (FEP) as a compression material allowsthe elements to be encapsulated between the inner body and coils 555,and the outer body when heated above the melt temperature of thematerial of the inner and outer portions of the body.

Alternatively, other modes of manufacture are possible and will beapparent to persons skilled in the art. In addition to the tensileelement 550, the delivery sheath 542 may include reinforcementstructures, such as coils 555 to prevent collapse of the delivery sheath542 during use thereof.

FIG. 21C shows an embodiment of a hub 543 of the delivery sheath 542.The hub 543 includes a distal, primary seal 556 having a slit 557 and aproximal secondary seal 558 having an aperture 559. The multiple sealsare provided in order to allow for a hemostatic seal where devices ofvarying sizes are directed into the hub 543 and delivery sheath 542. Inone embodiment, the proximal seal has a width 0.050″, while the distalseal has a width of 0.25″. The multi-stage seal is adapted to provide ahemostatic seal for a guidewire, which may have an outer diameter of0.035″, up to a cannula body, which may have an outer diameter up to0.5″, and possible even greater than 0.5″. The tubing 545 is distal ofthe primary and secondary seals 556, 558 at a point distal of the step574. The placement of the tubing 545 distal of the seals 556, 558 allowsthe hub 543 to maintain a hemostatic seal in the system while ventingthe delivery sheath 548. Tubing 545 may also be utilized for directingfluids into the system.

In one embodiment, the hub 543 comprises a multi-part assembly 560having a distal portion 562 and a proximal portion 564. The distalportion 562 includes the primary seal 556 and is fixedly coupled to thedelivery sheath 542. The distal portion 562 includes a section 566configured to receive the proximal portion 564 and maintain the positionof the proximal portion 564 relative thereto. In one embodiment, thedistal portion 562 and proximal portion 564 include threaded portions568, which threadably engage to thereby couple the distal and proximalportions 562, 564 together and maintain the position of the proximalportion 564 relative to the distal portion 562.

The hub 543 includes a first inner diameter 570 at the proximal portion564 sized to receive a loading device 578 (FIG. 22A). The distal portion562 of the hub 543 includes a second inner diameter 572 which is sizedto receive the loading device 578. The distal portion 562 of the hub 543includes a step 574 which is defined as a transition between the secondinner diameter 572 and a third inner diameter 576 of the hub. The thirdinner diameter 576 is the same or similar to the inner diameter 586(FIG. 22A) of the loading device 578 such that the anchors 518 a, 518 bremain folded when exiting from the loading device 578 and while beingdirected into the distal portion 562 of the hub 543.

FIG. 22A shows an alternative configuration of a loading device 578 ofthe delivery system as discussed herein. In the embodiment as shown inFIG. 22A, the loading device 578 is configured to receive the anchors518 a, 518 b in the contracted state and assist the delivery of thecannula assembly 500 into the delivery sheath 542 with the anchors 518a, 518 b in the contracted state.

The loading device 578 includes a distal end 580, a proximal end 582 anda lumen 584 therebetween. The distal end 580 has a first inner diameter586 and the proximal end 582 has a second inner diameter 588. The firstinner diameter 586 is smaller than the second inner diameter 588,thereby defining inner and outer stepped portions 590 a, 590 b in thelumen 584 and on the outer portion 591, respectively, between the distaland proximal ends 580, 582 of the lumen 584. The inner stepped portion590 a includes a taper 592 configured to prevent damage to the anchor518 when the loading device 578 receives the anchors 518 in thecontracted state.

The loading device 578 is used to fold the anchors 518 a, 518 b andintroduce the cannula assembly 500 into the hub 543 of the deliverysheath 542. To fold the anchors 518 a, 518 b, the cannula tip 514 isadvanced into and through the loading device 578 as shown in the FIG.22B, thereby folding both sets of anchors 518 a, 518 b in the proximaldirection. As shown in FIG. 22C, the distal anchors 518 b are allowed toexit the distal end 580 of the loading device 578 until they extend. Thecannula assembly 500 is then retracted slightly in the proximaldirection to fold the distal anchors 518 b distally and leaving theproximal anchors 518 a folded proximally. The loading device 578 is theninserted into the sheath hub 543 (FIG. 22E) through primary andsecondary seals 557, 558 and remains engaged with the hub 543 until thetip 514 of the cannula assembly 500 traverses past the distal, primaryseal 557. The loading device 578 is removed and the seals 557, 558provide a hemostatic seal on the cannula body 502. The inner diameter ofthe delivery sheath 542 may be the same or substantially similar as theinner diameter 586 of the loading device 578 to ensure a smoothtransition when advancing the cannula tip 514 out of the loading deviceand into the sheath 542.

The loading of the cannula assembly 500 to move the anchors 518 a, 518 binto a folded configuration may be completed without the aid offluoroscopy. Once the cannula assembly 500 resides within the sheath542, fluoroscopy may be used to aid the delivery of the cannula assembly500 to the septum 30. The taper 592 in the loading device 578 preventsdamage, such as tearing, of the anchors 518 a, 518 b as the anchors 518a, 518 b are directed into the loading device 578. The taper 592 furtherprevents tearing of the anchors 518 a, 518 b as the loading device 578is retracted from the hub 543 of the delivery sheath 542 and as thecannula assembly 500, with the anchors 518 in a contracted state, isdirected further into the delivery sheath 542.

FIG. 23A shows a typical configuration of a circulatory assist system,including a cannula assembly 500 for directing blood from the heart of apatient. More specifically, the distal end 506 of the cannula body 502is in fluid communication with the right atrium 14 of the heart 15. Thecannula body 502 traverses therefrom through the septum 30, up throughthe superior vena cava 16 and into the subclavian vein 18. At a point inthe subclavian vein 18, the cannula body 502 exits therefrom and theproximal end 504 of the cannula body 502 is fluidicly communicated withan inlet portion 596 of a pump 594. The outlet 598 of the pump 594 is influid communication with an outflow cannula 600. The outflow cannula 600communicates with the subclavian artery 40, into which blood is directedfrom the outflow cannula 600 as the outflow cannula 600 receives bloodfrom the pump 594. In the configuration shown in FIG. 23B, the outflowcannula 600 is positioned over, or posterior to, the subclavian vein.However, depending on the anatomy of a specific patient, the outflowcannula 600 may be placed behind, or anterior to, the subclavian vein18. In this configuration, the pump 594 is disposed such that the inletportion 596 is facing a generally medial direction, or towards thecenter of the body of the patient 20. Blood flows in the direction ofarrows 42.

FIG. 23B shows the configuration of a circulatory assist system whichincludes a cannula adaptor 602. Similar to the configuration as shown inFIG. 23A, the distal end 506 of the cannula body 502 is in fluidcommunication with the right atrium 14 of the heart 15. The cannula body502 traverses therefrom through the septum 30, up through the superiorvena cava 16 and into the subclavian vein 18. However, at a point in thesubclavian vein 18, the cannula body 502 exits and, instead of beingcoupled directly with the inlet portion 596, the proximal end 504 of thecannula body 502 is coupled to the distal end 604 of the cannula adaptor602. The proximal end 606 of the cannula adaptor 602 then couples withthe inlet portion 596 of the pump 594. In this configuration utilizingthe cannula adaptor 602, the inlet portion 596 of the pump 594 is facingin a generally lateral direction, or facing generally away from thecenter of the body of the patient 20. The outlet 598 of the pump 594fluidicly communicates with an outflow cannula 600. The outflow cannula600 then fluidicly communicates with the subclavian artery 40. Bloodflows in the direction of arrows 42.

The cannula adaptor 602 is provided for multiple potential advantageousreasons. The cannula adaptor 602 reduces stress on the subclavian vein18. Rather than bending the cannula body 502 to reach the inlet 596 ofthe pump 594 and thereby stressing the vein 18 at the point where thecannula body 502 exits therefrom, the cannula adaptor 602 is providedwith an essentially curvilinear shape to reach the inlet 596 of the pump594.

As shown more specifically in FIGS. 23C-23D, the cannula adaptor 602further comprises a distal end 604, a proximal end 606 and a body 608therebetween. The distal end 604 of the cannula adaptor 602 couples withthe proximal end 504 of the cannula body 502. To facilitate theconnection, the distal end 604 of the adaptor device 602 furthercomprises a fitting 610 adapted to receive the proximal end 504 of thecannula body 502. Furthermore, a swaged or crimped band 612 may beprovided on the cannula adaptor 602 to provide further resistanceagainst the undesired removal of the cannula body 502 from the fitting610 of the cannula adaptor 602. The proximal end 606 of the adaptordevice 602 couples with the inlet 574 of the pump 594. In oneembodiment, the proximal and distal ends 606, 604 of the cannula adaptor602 may connect to the pump 594 and the cannula body 502, respectively,using connections not requiring additional fasteners or suturestherebetween. For example, the proximal end 606 of the cannula adaptor602 may connect to the pump inlet 596 in a snapping or ratchetingfashion.

The cannula adaptor 602 comprises a generally curvilinear shape, whichenables the configuration as shown in FIG. 23B. For advantageous fluidflow, the body 608 includes a taper between the proximal and distal ends606, 604, where the taper is defined as a decrease in diameter from thefirst diameter 614 to the second diameter 616 between the proximal anddistal ends 606, 604. More specifically, the tapered configuration ofthe body, and thus the lumen therein (not shown) is provided to preventcavitation in the pump 594 as the pressure decreases along the length ofthe cannula adaptor 602. In one embodiment, the decrease in diameter isconstant along the tapered portion.

Further, advantageously, the tapered configuration of the cannulaadaptor 602 further allows for a relatively smaller cannula body 502 tobe used during a procedure, while still utilizing existing and/orcurrently utilized pumps 594. The proximal end 504 of the cannula body502 is therefore preferably sized to couple to a blood pump known in theart, such as the CircuLite SYNERGY™ Pump. Therefore, because a smallersize cannula body 502 is able to be used, the cannula adaptor 602enables use of the transseptal device and method described herein with awider variety of procedures and patients. Utilizing a smaller sizecannula body 502, for example, may lessen the constraints of thedelivery thereof through the venous system.

While the present invention has been illustrated by a description ofvarious preferred embodiments and while these embodiments have beendescribed in some detail, it is not the intention of the Applicants torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. The various features of the invention may beused alone or in any combination depending on the needs and preferencesof the user. This has been a description of the present invention, alongwith the preferred methods of practicing the present invention ascurrently known. However, the invention itself should only be defined bythe appended claims.

The invention claimed is:
 1. A circulatory assist system, comprising: acannula assembly, further comprising: a cannula body for directing bloodfrom the heart of a patient, having distal and proximal ends and a lumentherebetween; and a unitary rigid tip coupled to the distal end of thebody, the unitary rigid tip having an opening; a pump for drawing bloodinto the cannula assembly and dispensing the blood from the cannulaassembly and into the patient circulatory system; wherein the lumen ofthe cannula body further comprises: a first inner diameter at theproximal end and a second inner diameter at the distal end, the firstinner diameter being larger than the second inner diameter, and atapered portion defined as a decrease in inner diameter from the firstinner diameter to the second inner diameter between the proximal anddistal ends, the tapered portion configured to prevent cavitation of theblood within the cannula.
 2. The circulatory system of claim 1, whereinthe decrease in inner diameter is constant between the proximal anddistal ends.
 3. The circulatory assist system of claim 2, wherein thedecrease in inner diameter occurs along only a portion of the lumen. 4.A circulatory assist system, comprising: a cannula body having distaland proximal ends and a lumen therebetween; a pump for drawing bloodinto the cannula body and dispensing the blood from the cannula assemblyand into the patient circulatory system; and a unitary rigid tip at thedistal end of the cannula body in fluid communication with the lumen andconfigured to communicate the lumen with a cavity of the heart, theunitary rigid tip including a distal portion having first and secondends having first and second diameters, respectively, the second endmore distal than the first end, and the second diameter larger than thefirst diameter, wherein the unitary rigid tip is configured to prevent adrop of pressure of blood entering the unitary rigid tip and travelingthrough the cannula.
 5. The circulatory assist system of claim 4,wherein the distal portion of the unitary rigid tip is defined as agenerally campanulate shape.
 6. The circulatory assist system of claim4, wherein the second diameter of the unitary rigid tip is about equalto an outer diameter of the distal end of the cannula assembly.
 7. Acirculatory assist system, comprising: a cannula assembly having distaland proximal ends and a lumen therebetween; a pump for drawing bloodinto the cannula assembly and dispensing the blood from the cannulaassembly and into the patient circulatory system; and a delivery sheathfor delivering the cannula assembly through the patient circulatorysystem, wherein the delivery sheath is configured to receive the cannulaassembly and move relative thereto for deploying the cannula assemblyadjacent a heart cavity and further comprises a distal end, a proximalend, and a body therebetween; wherein the body further comprises alongitudinally disposed tensile element embedded therein and configuredto prevent deformation of the body when the cannula assembly movesrelative to the delivery sheath.
 8. The delivery system of claim 7,wherein the longitudinally disposed element is configured to preventplastic deformation of the delivery sheath in a substantially axialdirection.
 9. The delivery system of claim 7, wherein the deliverysheath further comprises an inner wall defining a passage for receivingthe cannula assembly, and an outer wall, and the longitudinally disposedtensile element is disposed between the inner and outer walls of thedelivery sheath.
 10. The delivery system of claim 7, wherein thelongitudinally disposed element comprises at least one of the following:a monofilament or polyfilament.
 11. The delivery system of claim 10,wherein the longitudinally disposed element further comprises at leastone of the following: metal, fabric, or polymer.
 12. A delivery systemfor delivering a cannula assembly, including an anchor to the heart of apatient, the anchor having contracted and expanded states, the deliverysystem comprising: a delivery sheath, the sheath configured to receivethe cannula assembly and move relative thereto for deploying the anchorinto the expanded state; and a loading device configured to receive theanchor in the contracted state and assist the delivery of the cannulaassembly into the delivery sheath with the anchor in the contractedstate, and further comprising: a proximal end, a distal end and a lumentherebetween, the proximal end having a first inner diameter and thedistal end having a second inner diameter, the first inner diameterbeing larger than the second inner diameter; and a stepped portion inthe lumen where the first inner diameter changes to the second innerdiameter, and a taper at the stepped portion, defined as a decrease ininner diameter between the first inner diameter and the second innerdiameter, the taper configured to prevent damage to the anchor when thedelivery sheath receives the cannula assembly.
 13. A circulatory assistsystem for assisting the flow of blood through a patient circulatorysystem, comprising: a cannula assembly for directing blood from theheart of a patient, the cannula assembly comprising a flexible cannulabody including a proximal end and a distal end and a lumen therebetween;a pump for drawing blood from the heart into the cannula assembly anddispensing the blood from the cannula assembly and into the patientcirculatory system, the pump further including an inlet and an outlet;an outflow cannula configured to fluidicly communicate the outlet and anartery of a patient; and an adaptor device configured to fluidiclycommunicate the inlet and the cannula body, the adaptor device includinga proximal end, a distal end, and a lumen therebetween; wherein thedistal end of the adaptor device is configured to couple with theproximal end of the cannula body and the proximal end of the adaptordevice is configured to couple with the inlet of the pump; wherein theadaptor device is generally curvilinear such that blood flowing into thedistal end of the adaptor device flows in a generally lateral directionrelative to the patient and blood flowing out of the proximal end of theadaptor device and into the inlet flows in a generally medial directionrelative to the patient.
 14. The circulatory assist system of claim 13,wherein the artery is a subclavian artery.
 15. The circulatory assistsystem of claim 13, wherein the lumen of the adaptor device includes atapered portion between the proximal and distal ends, the taperedportion defined as a decrease in inner diameter from a first innerdiameter to a second inner diameter between the proximal and distalends, respectively.
 16. The circulatory assist system of claim 13,wherein the distal end of the adaptor device further comprises a fittingadapted to receive the proximal end of the cannula assembly.
 17. Thecirculatory assist system of claim 15, wherein the decrease in innerdiameter is constant along the tapered portion.
 18. A method ofdeploying a circulatory assist system into a circulatory system of apatient, the circulatory assist system including a cannula assembly anda pump, the assist system for assisting the flow of blood through thecirculatory system, comprising: directing a cannula assembly into thecirculatory system of a patient, wherein a distal end of the cannulaassembly extends into a chamber of the heart, and the proximal end ofthe cannula assembly extends in a generally lateral direction therefrom;implanting a pump having an inlet and an outlet such that the inletfaces in a generally lateral direction relative to the patient;fluidicly communicating the outlet of the pump with an artery using anoutflow cannula; coupling a proximal end of the cannula assembly with adistal portion of an adaptor device; coupling a proximal portion of theadaptor device with the inlet of the pump; wherein the adaptor device isgenerally curvilinear such that blood flowing into the distal end of theadaptor device flows in a generally lateral direction relative to thepatient, and blood flowing out of the proximal end of the adaptor deviceand into the inlet flows in a generally medial direction relative to thepatient.
 19. The method of claim 18, wherein the artery is a subclavianartery.